Non-Telecentric Light Guide Elements

ABSTRACT

The present disclosure relates to systems and methods relating to the fabrication of light guide elements. An example system includes an optical component configured to direct light emitted by a light source to illuminate a photoresist material at one or more desired angles so as to expose an angled structure in the photoresist material. The photoresist material overlays at least a portion of a first surface of a substrate. The optical component includes a container containing a light-coupling material that is selected based in part on the one or more desired angles. The system also includes a reflective surface arranged to reflect at least a first portion of the emitted light to illuminate the photoresist material at the one or more desired angles.

BACKGROUND

Light guiding devices may include optical fibers, waveguides, and otheroptical elements (e.g., lenses, mirrors, prisms, etc.). Such lightguiding devices may transmit light from an input facet to an outputfacet via total or partial internal reflection. Furthermore, lightguiding devices may include active and passive optical components, suchas optical switches, combiners, and splitters.

Optical systems may utilize light guiding devices for a variety ofpurposes. For example, optical fibers may be implemented to transmitoptical signals from a light source to a desired location. In the caseof light detection and ranging (LIDAR) devices, a plurality of lightsources may emit light, which may be optically coupled to the lightguiding devices so as to be directed into a given environment. The lightemitted into the environment may be detected by a receiver of the LIDARdevices so as to provide estimated distances to objects in theenvironment.

SUMMARY

The present disclosure relates to systems and methods of manufacturerelating to light guiding elements configured to be mounted in anon-telecentric arrangement within an optical system. Additionally oralternatively, systems and methods described herein could be applicableto the manufacture of optical systems. For example, the presentdisclosure describes certain optical elements (e.g., light guidedevices) and methods for their manufacture. The optical waveguides mayinclude one or more structures such as mirrored surfaces, verticalstructures, and/or angled structures.

In a first aspect, a system is provided. The system includes an opticalcomponent configured to direct light emitted by a light source toilluminate a photoresist material at one or more desired angles so as toexpose an angled structure in the photoresist material. The photoresistmaterial overlays at least a portion of a first surface of a substrate.The optical component includes a container containing a light-couplingmaterial that is selected based in part on the one or more desiredangles. The system also includes a reflective surface arranged toreflect at least a first portion of the emitted light to illuminate thephotoresist material at the one or more desired angles.

In a second aspect, an optical system is provided. The optical systemincludes a substrate and a light-emitter device. The optical system alsoincludes an optical waveguide arranged along a surface of the substrate.The optical waveguide includes a mirror portion. The optical waveguideis configured to guide light emitted by the light-emitter device. Aportion of the guided light interacts with the mirror portion so as todirect reflected light into an environment of the optical system. Themirror portion includes a reflective surface arranged between 30 degreesand 60 degrees with respect to the substrate.

In a third aspect, a method is provided. The method includes placing asubstrate near one end of an optical component. The photoresist materialoverlays at least a portion of a first surface of the substrate. Theoptical component includes: (i) a container containing a light-couplingmaterial, and (ii) a reflective surface. The method also includescausing a light source to emit light into the optical component. Thereflective surface reflects at least a first portion of the emittedlight to illuminate the photoresist material at one or more desiredangles, thereby exposing at least a portion of an angled structure inthe photoresist material.

Other aspects, embodiments, and implementations will become apparent tothose of ordinary skill in the art by reading the following detaileddescription, with reference where appropriate to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a system, according to an example embodiment.

FIG. 2A illustrates a system, according to an example embodiment.

FIG. 2B illustrates an aperture mask of the system of FIG. 2A, accordingto an example embodiment.

FIG. 2C illustrates various reflective surface types, according toexample embodiments.

FIG. 2D illustrates a photoresist structure, according to an exampleembodiment.

FIG. 2E illustrates an optical component, according to an exampleembodiment.

FIG. 2F illustrates an optical component, according to an exampleembodiment.

FIG. 3A illustrates a system, according to an example embodiment.

FIG. 3B illustrates a system, according to an example embodiment.

FIG. 3C illustrates a system, according to an example embodiment.

FIG. 4A illustrates an optical system, according to an exampleembodiment.

FIG. 4B illustrates an optical system, according to an exampleembodiment.

FIG. 5 illustrates a method, according to an example embodiment.

DETAILED DESCRIPTION

Example methods, devices, and systems are described herein. It should beunderstood that the words “example” and “exemplary” are used herein tomean “serving as an example, instance, or illustration.” Any embodimentor feature described herein as being an “example” or “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments or features. Other embodiments can be utilized, and otherchanges can be made, without departing from the scope of the subjectmatter presented herein.

Thus, the example embodiments described herein are not meant to belimiting. Aspects of the present disclosure, as generally describedherein, and illustrated in the figures, can be arranged, substituted,combined, separated, and designed in a wide variety of differentconfigurations, all of which are contemplated herein.

Further, unless context suggests otherwise, the features illustrated ineach of the figures may be used in combination with one another. Thus,the figures should be generally viewed as component aspects of one ormore overall embodiments, with the understanding that not allillustrated features are necessary for each embodiment.

I. Overview

Light guides may include optical elements that may be configured toguide light within the light guides. These optical elements may includestructures that may reflect light (totally or partially) in order totransmit light from an input facet to an output facet of the lightguide. For example, the optical elements may be vertical and/or angledstructures that may guide light. More specifically, a vertical structuremay guide light along a length of the structure. An angled structure maybe coated with a metal that is optically reflective, thereby effectivelyfunctioning as a mirror that may reflect incident light in a particulardirection.

In an example embodiment, light guides may be formed from a photoresistmaterial and may be configured to guide infrared light.

In practice, light guides may be fabricated using photolithography,which uses a light source to expose structures of the optical elementsin a photoresist material that overlays a substrate. The desiredstructures may be exposed by exposure light that illuminates thephotoresist with a photomask pattern. In such scenarios, verticalstructures are exposed by exposure light that is normally incident onthe photoresist material so as to expose the photoresist at a normalangle.

On the other hand, angled structures are exposed by exposure light thatis incident on the photoresist material at a non-normal angle. Forexample, to expose an angled structure, a refractive angle of the lightin the photoresist material is set at a desired angle of the angledstructure. However, achieving some refractive angles in the photoresistmaterial can be challenging. For instance, when a medium between thelight source and the photoresist material is air, the refractive anglein the photoresist material to expose some angled structures may not beachievable according to Snell's law.

One current solution is to use immersion photolithography to achieve thedesired refractive angles in the photoresist material. In this solution,the substrate may be immersed in a medium that has a moderate refractiveindex. The material is chosen to have an index high enough to transmitlight that refracts to the designed angles in the photoresist materialaccording to Snell's law. To expose angled structures in the immersedphotoresist material, a robotic device moves a light source at specificangles with respect to the photoresist material to expose thephotoresist material at the desired angles. Although this solution maybe used to fabricate angled structures, it is inefficient andtime-consuming. In practice, fabricating optical elements using such atechnique may take several hours.

Disclosed herein are immersion lithography systems and methods thatcould include an optical component configured to direct light from alight source to illuminate a photoresist material on a substrate at aplurality of desired angles and thereby expose a plurality ofvariously-angled structures in the photoresist material. The opticalcomponent may include a container containing an index-matching material(e.g., water or another fluid) that is selected based in part on thedesired angles. The optical component may also include a reflectivesurface arranged to reflect at least a portion of the light toilluminate the photoresist material at the desired angles.

In an example embodiment, the reflective surface includes a plurality ofdifferent angles that can form the plurality of desired angles in thephotoresist material. In such scenarios, the angled structures can beformed with different controllable angles, which are determined based ona shape of the reflective surface.

In some embodiments, the angled structures could be coated with areflective material so as to form angled mirror structures. The angledmirror structures could be optically coupled to a respective pluralityof light guides (e.g., optical waveguides). A plurality of light emitterdevices could be configured to emit respective light pulses along thelight guides. The light pulses could be guided along the light guidesand reflected out-of-plane by the angled mirror structures. In suchscenarios, the light pulses could be emitted into an environment atdifferent angles.

A LIDAR system could include a plurality of light emitter devices and alight guide manifold. The light guide manifold could include a pluralityof waveguides corresponding, and optically-coupled, to the respectivelight emitter devices. The plurality of light emitter devices could beconfigured to emit light pulses along the respective waveguides. Thelight guide manifold may also include a plurality of angled mirrorstructures optically coupled to the waveguides. In an exampleembodiment, the plurality of angled mirror structures could beconfigured to direct the light pulses out of the plane of the waveguidesand toward an environment of the LIDAR. Furthermore, the respectiveangle of the angled mirror structures could be different so that thelight pulses are controllably directed along different emission anglestoward the environment. For example, the angled mirror structures couldbe arranged at 42 degrees, 45 degrees, and 48 degrees with respect tothe plane of the waveguides. However, other angles and/or angle rangesare contemplated and possible.

II. Example Systems

In line with the discussion above, some desired structures can bechallenging to fabricate using current photolithography systems. Forinstance, fabricating some angled structures may not be feasible whenthe medium between the light source and the photoresist material is air.Specifically, according to Snell's law, the angles of refraction in thephotoresist material to expose the angled structures may not beachievable when the medium between the light source and the photoresistmaterial is air.

Disclosed herein are methods and systems for fabricating opticalelements (e.g., optical waveguides). In particular, the methods andsystems may be used to fabricate optical elements that include desiredstructures (e.g., desired angled and/or vertical structures). Further,the methods and systems disclosed herein may fabricate optical elementsmore rapidly and efficiently than fabrication systems currently used inpractice.

FIG. 1 illustrates a system 100, according to an example embodiment. Thesystem 100 may be a photolithography system that may be configured tofabricate optical elements by exposing desired structures in aphoto-patternable material. Furthermore, the system 100 could beutilized in the context of optical immersion lithography. In suchscenarios, the system 100 could be used to form angled structures atdesired angles in a photoresist material.

The system 100 includes an optical component 110 configured to directlight 12 emitted by a light source 10 to illuminate a photoresistmaterial 130 at one or more desired angles so as to expose an angledstructure 134 in the photoresist material 130. As explained herein, theoptical component 110 may be configured to manipulate light emitted bythe light source 10 in order to expose the desired structures in thephotoresist material 130.

In such embodiments, the photoresist material 130 overlays at least aportion of a first surface 142 of a substrate 140. For example, thephotoresist material 130 may include SU-8 polymer, Kloe K-CL negativephotoresist, Dow PHOTOPOSIT negative photoresist, or JSR negative toneTHB photoresist. It will be understood that the photoresist material 130may be include other polymeric photo-patternable materials.

The substrate 140 may be a transparent substrate such as glass and/oranother material that is substantially transparent to a desiredwavelength range (e.g., near infrared wavelengths or another infraredwavelength range).

In some embodiments, the light source 10 may be configured to emit oneor more wavelengths of light. For instance, the light source 10 may beconfigured to emit visible light and/or ultraviolet (UV) light.Furthermore, the light source 10 may include one or more components(e.g., a lens and/or a collimator) that may enable the light source 10to emit collimated or substantially collimated light. For instance, thelight may be collimated using anisotropic collimation. In suchscenarios, the light source 10 could be an anisotropic collimated lightsource.

In some embodiments, the light source 10 may emit p-polarized light inorder to reduce reflections from the substrate-resist interface and froma back-side of the substrate 140. Accordingly, the light source 10 mayinclude a polarizer (e.g., a polarization filter) that enables the lightsource 10 to emit p-polarized light. Additionally and/or alternatively,the light source 10 may include an integrated timer, which may allow thesystem 100 to control an exposure time. In an example implementation,the light source 10 may be a 500 Watt UV lamp source. In another exampleimplementation, the light source 10 may be a 500 Watt collimated UV lampsource.

Additionally or alternatively, the light source 10 could be a mercury orxenon gas discharge lamp. In other embodiments, the light source 10could be a deep ultraviolet (UV) excimer laser, such as a 193 nm ArFexcimer laser. However, other light sources suitable for opticallithography and/or immersion lithography are possible and contemplated.

In an embodiment, the optical component 110 may be configured tomanipulate the emitted light in order to expose the photoresist material130. To manipulate the emitted light, the optical component 110 may belocated in proximity of and optically coupled to the light source 10. Inan implementation, the optical component 110 may be located above orbeneath the light source 10, with respect to a level surface. Otherorientations of the optical component 110 and the light source 10 arecontemplated and possible.

The optical component 110 includes a container 112 containing alight-coupling material 114 that is selected based, in part, on the oneor more desired angles. In an example embodiment, the light-couplingmaterial 114 may include a liquid medium (e.g., purified water) that hasa refractive index greater than one. In other examples, thelight-coupling material 114 may be glycol (refractive index˜1.43) and/orglycerol (refractive index˜1.47), among other examples. In an example,the light-coupling material 114 may be any material that has arefractive index appropriate to support transmission of light rayswhich, after refraction, have the desired angle in the photoresist.Additionally or alternatively, the light-coupling material 114 may be asolid (e.g., clear acrylic and cured silicone or epoxy), liquid,adhesive, or gel that fills at least a portion of an interior of thecontainer 112. However, other types of light-coupling materials commonto immersion lithography are possible and considered herein.

In some embodiments, the container 112 may be made from one or morematerials, such as aluminum and/or other types of metal. A portion ofone surface of the container 112 may be transparent so that the lightemitted by light source 10 may enter the container 112. A portion ofanother surface of the container 112 may also be transparent in orderfor light to exit the container 112 to expose the photoresist material130. For example, portions of a top surface and a bottom surface of thecontainer 112 may be transparent in order for light to enter/exit thecontainer 112. Notably, the transparent portions may be transparent tothe type of emitted light. For instance, when the emitted light is UVlight, the transparent portions may be transparent to UV light. Examplematerials of the transparent portions may include glass and/or any othermaterial that is transparent to the light emitted by light source 10.

The optical component 110 additionally includes a reflective surface 116arranged to reflect at least a first portion of the light 14 toilluminate the photoresist material 130 at the one or more desiredangles. In example embodiments, the reflective surface 116 may include asurface mirror, a concave mirror, a convex mirror, a prism, and/or adiffractive mirror. In some embodiments, the optical component 110 mayinclude a plurality of reflective surfaces 116. In such scenarios, thereflective surfaces 116 may include mirrors of the same type,orientation, and/or characteristics.

In some embodiments, the one or more desired angles could include atleast one of: 42 degrees, 45 degrees, and 48 degrees with respect to thefirst surface 142. In such a manner, the photoresist material 130 couldbe exposed with UV light and developed so as to form a plurality ofangled structures 134. However, it will be understood that the angledstructures 134 could have surfaces having other angles with respect tothe first surface 142. For example, the one or more desired angles couldinclude at least one angle selected from an angle range between 40degrees and 60 degrees with respect to the first surface 142.

In some embodiments, the reflective surface 116 could include aplurality of flat mirror portions 118 corresponding to the one or moredesired angles.

Additionally or alternatively, the reflective surface 116 could includeone or more curved mirror portions 119.

In some embodiments, system 100 could further include an aperture mask160 placed between the light source 10 and the substrate 140. Theaperture mask 160 includes one or more openings 162, each openingcorresponding to a respective desired structure (e.g., verticalstructures 132 and/or angled structures 134) in the photoresist material130. At least a portion of the emitted light that is transmitted througheach opening exposes the respective desired structure to which theopening corresponds. As an example, the respective desired structurecould include at least one vertical structure 132 and at least oneangled structure 134.

In an embodiment, each of the openings 162 of the aperture mask 160 maycorrespond to a respective desired feature for exposure in thephotoresist material 130. The aperture mask 160 may be used to definethe approximate fields of different angles of exposure light byselectively allowing light to pass through the mask's openings. Eachopening may allow a respective portion of light to pass through, whichmay then be used (directly or indirectly) to expose a particular featurein the photoresist material 130.

For example, the aperture mask 160 includes a first opening. In suchscenarios, the first opening is configured to allow the first portion ofthe emitted light to interact with a first portion of the reflectivesurface 116. The first portion of the reflective surface 116 isconfigured to redirect the first portion of the emitted light 14 toexpose the at least one angled structure 134.

In some embodiments, the aperture mask 160 includes a second opening. Insuch scenarios, the second opening is configured to allow a secondportion of the emitted light 16 to expose the at least one verticalstructure 132.

In various embodiments, the aperture mask 160 could include one or moreneutral density filters configured to reflect and/or absorb light so asto balance the light intensity incident onto the normal and angled fieldregions of the photoresist material 130. One such neutral density filtercould include incorporating a pattern of small opaque and/or clearcircles on the opposite background (e.g., a polka dot pattern) to theaperture mask 160. In such a scenario, the light transmitted throughsuch a neutral density filter may be uniformly attenuated uponinteraction with the photoresist material 130. Additionally, due todiffraction, the light could be slightly blurred. The input light to thesystem is not collimated perfectly and may have an angular range of 1-2degrees. Accordingly, the dot pattern may be blurred into a uniformintensity at a sufficient “throw” distance, approximately the dot perioddivided by the tangent of the angular range. In some embodiments, for afine pattern under 1 mm period, the blurring may occur oversubstantially the entire width of the optics box (e.g., 50 mm).Accordingly, light transmitted through the neutral density filter regioncould be substantially blurred so as to form a uniform illuminationintensity at the photoresist material 130.

In example embodiments, at least a portion of a first surface and atleast a portion of a second surface of the container 112 aretransparent. In such scenarios, the emitted light 12 enters thecontainer 112 through the transparent portion of the first surface, andwherein the emitted light illuminates the photoresist material 130through the transparent portion of the second surface.

In various embodiments, system 100 could include a photomask 170. Insome embodiments, the photomask 170 is arranged in proximity to thephotoresist material 130. The photomask 170 is configured to defineindividual desired structures in the photoresist material 130.

In various embodiments, the photomask 170 may be located near thesubstrate 140, perhaps placed above the photoresist material 130. In anembodiment, the photomask 170 may be used to define individualstructures in the photoresist material 130. In particular, the photomask170 may include a pattern of openings or transparencies that allowexposure light to transmit through to the photoresist material 130. 5Inan embodiment, the pattern may correspond to a desired arrangement ofoptical waveguides or other structures formed from the photoresistmaterial 130. That is, the photomask 170 may include openings thatcorrespond to vertical structures 132 and/or angled structures 134. Whenthe substrate 140 is exposed with light, the light that is transmittedthrough an opening that corresponds to a vertical structure creates avertical structure in the photoresist material 130, and the light thatis transmitted through an opening that corresponds to an angledstructure may create an angled structure 134 in the photoresist material130 (upon photoresist bake and/or development processes). As explainedherein, light that is reflected from the reflective surface 116 may betransmitted through the openings of the photomask 170 that correspond tothe angled structures 134.

In some embodiments, the optical component 110 further includes a deviceconfigured to remove stray light within the optical component 110. Forexample, the optical component 110 could include a light baffle oranother type of light-noise-mitigating structure and/or material.

In various examples, an optical absorber could be disposed behind thesubstrate 140 (e.g., along a surface opposite the photoresist material130). The optical absorber may be configured to prevent backscatteredlight from causing spurious patterns in the photoresist material 130.The optical absorber could include a coating on the back of thesubstrate 140. Alternatively, the optical absorber could be a dark oropaque material that is separate from the substrate 140. For example, anoptical coupling material (e.g., the light-coupling material 114) couldbe disposed between the back of the substrate 140 and the opticalabsorber.

In some embodiments, the substrate 140 could be immersed in thelight-coupling material 114 such that the photoresist material 130 isfacing a second surface of the container 112. At least a portion of thesecond surface of the container 112 is transparent. In such a scenario,the emitted light 12 from the light source 10 enters the container 112through the transparent portion of the second surface of the container112.

FIG. 2A illustrates a system 200, according to an example embodiment.The system 200 could be similar or identical to system 100, asillustrated and described in relation to FIG. 1. For example, a lightsource 10 could be configured to emit light 12 toward an opticalcomponent 110.

In an example embodiment, the light 12 could interact with an aperturemask 160. In such a scenario, light portions 12 a, 12 b, 12 c, and 12 dmay pass substantially through respective openings 162 a, 162 b, 162 c,and 162 d in the aperture mask 160.

Light portion 12 a could interact with reflective surface 116 a, whichmay be arranged along a flat mirror portion 118 a. Reflective surface116 a could be arranged at an angle θ_(a) with respect to support 210 aor another reference plane of the container 112. In such a scenario,light portion 12 a could be reflected from reflective surface 116 a asreflected light 212 a. Reflected light 212 a may interact withphotoresist material 130 along an angle (e.g., 42°) with respect tosubstrate 140 and first surface 142. In such a scenario, reflected light212 a may expose the photoresist material 130 with UV light so as tocross-link the photoresist material 130. In so doing, the reflectedlight 212 a may help form angled structure 134 a within the context of aphotoresist exposure and development process.

Likewise, light portions 12 b and 12 c may interact with reflectivesurfaces 116 b and 116 c, respectively. For example, light portion 12 bcould interact with reflective surface 116 b, which could be arrangedalong a flat mirror portion 118 b. In such a scenario, reflectivesurface 116 b could be arranged at an angle θ_(b) with respect tosupport 210 b or another reference plane or surface of the container112. In an example embodiment, light portion 12 b could be reflectedfrom reflective surface 116 b as reflected light 212 b. Reflected light212 b may interact with photoresist material 130 along an angle (e.g.,45°) with respect to substrate 140 and first surface 142. In examples,reflected light 212 b may expose the photoresist material 130 with UVlight, cross-linking it. As such, the reflected light 212 b may form, atleast in part, angled structure 134 b within the context of aphotoresist exposure and development process.

Additionally or alternatively, light portion 12 c could interact withreflective surface 116 c, which could be arranged along a flat mirrorportion 118 c. In such a scenario, reflective surface 116 c could bearranged at an angle θ_(c) with respect to support 210 c or anotherreference plane or surface of the container 112. In an exampleembodiment, light portion 12 c could be reflected from reflectivesurface 116 c as reflected light 212 c. Reflected light 212 c mayinteract with photoresist material 130 along an angle (e.g., 48°) withrespect to substrate 140 and first surface 142. In examples, reflectedlight 212 c may expose the photoresist material 130, cross-linking it.In such a manner, the reflected light 212 c may help, at least in part,form angled structure 134 c in a photoresist exposure and developmentprocess.

In some embodiments, light portion 12 d could pass through the apertureplate 160 via opening 162 d. In such cases, light portion 12 d couldpass directly (e.g., vertically or straight) toward the photoresistmaterial 130 and substrate 140. In examples, light portion 12 d couldexpose the photoresist along a vertical (e.g., normal) angle withrespect to the substrate 140. In such scenarios, light portion 12 dcould assist to form vertical structures 132 in the photoresist material130 upon a photoresist development process.

While not illustrated, the optical component 110 may also includestructures and/or devices for removing stray light. The structures maybe dark baffles that are arranged in the optical component 110 in orderto remove stray light (e.g., light reflected back into the opticalcomponent 110).

In some examples, an exterior of the container 112 may include plumbingfittings for filling and draining the light-coupling material 114 fromthe container 112. In another example embodiment, the container 112 mayinclude fittings for components (e.g., filters, vacuum devices, etc.) toremove air bubbles or other types of gas bubbles or impurities.Furthermore, in some embodiments, at least a portion of each of thereflective surface (e.g., reflective surfaces 116 a, 116 b, and/or 116c) may be masked in order to improve directivity of the light reflectedoff of the reflective surfaces.

In other embodiments, the system 200 may also include mechanical and/oroptical features for aligning the substrate 140 to the optical component110 and/or the light source 10. In an example, the system 200 mayinclude stages, fixtures, optical devices (e.g., magnifying devices),and/or image capturing devices (e.g., cameras) that may be used to alignthe substrate 140. In an implementation, the system 200 may include alinear stage that may be used to bring the substrate 140 in contact withan exit surface (e.g., bottom surface 214) with a light-couplingmaterial filling a gap between the exit surface and the substrate 140.Additionally, the exit surface may include fiducials that could be usedto align the substrate 140. For example, in-plane and rotation alignmentmay be achieved by aligning fiducial marks on the exit surface withfeatures on the photomask 170. In an implementation, two pairs offeatures may be observed simultaneously with one or more camerasarranged to image fiducial marks on the photomask 170 with respect tofiducial marks on the container 112.

FIG. 2B illustrates a top view of an aperture mask 160 of the system 200of FIG. 2A, according to an example embodiment. The aperture mask 160may include opaque features and transparent features that allow light topass through. For example, the aperture mask 160 could include aplurality of openings 162. For example, the openings 162 could includeseveral long, narrow transparent (or clear) openings 162 a, 162 b, 162c, and 162 d in the aperture mask 160.

In some cases, it may be desirable to overlap normal and angledillumination fields at the photoresist material 130 while maintaining asubstantially uniform illumination intensity in overlapping transitionregion. In such scenarios, the photoresist material 130 could beilluminated such that the intensity of one field increases along adirection which the intensity of the adjacent field decreases. In such afashion, as illustrated in inset 216, some or all edge features ofaperture mask 160 could include one or more gradient neutral densityfilters. In some embodiments, such filters may be configured to blur outto a gradient intensity pattern at the photoresist material 130.

For example, an optical gradient intensity filter could be implementedwith an opaque fine saw tooth pattern 218 along the edges of theaperture mask opening 162. Additionally or alternatively, the opticalgradient intensity filter could be provided by modulating a size and/ordensity of opaque circles (e.g., stippling or “polka dots”) along anedge feature of aperture mask 160. Embodiments could utilize these sawtooth and/or polka dot patterns mechanically as part of the edge ofaperture mask 160 or as part of a separate photomask aligned to theaperture mask 160 or fiducial marks on the substrate 140. While FIG. 2Billustrates all sides of opening 162 d as having a saw tooth pattern,other designs are possible. For example, in some embodiments, only onelong side of the opening could have the sawtooth pattern. In suchscenarios, the other sides of the opening could be straight (e.g.,unpatterned).

FIG. 2C illustrates various reflective surface types 220, 230, and 240,according to example embodiments. Reflective surface type 220 couldinclude a plurality of reflective surfaces 116 a, 116 b, and 116 c. Insuch a scenario, the reflective surfaces could include a first flatmirror portion 118 a, a second flat mirror portion 118 b, and a thirdflat mirror portion 118 c. Each of the flat mirror portions could bephysically separated from one another.

The reflective surfaces 116 a, 116 b, and 116 c could be mounted to thecontainer by way of one or more supports 210 a, 210 b, and 210 c. Thesupports 210 a, 210 b, and 210 c could be fixed so as to maintain anorientation of the reflective surfaces 116 a, 116 b, and 116 c at apredetermined angle or predetermined orientation. Additionally oralternatively, the supports 210 a, 210 b, and 210 c could be adjustableto adjust the orientation of the reflective surfaces 116 a, 116 b, and116 c. For example, one or all of supports 210 a, 210 b, and 210 c couldbe configured to be adjustable by way of a piezoelectric actuator, astepper motor, or another type of angle-adjustment apparatus. It will beunderstood that there are many other ways to adjust an orientation ofthe reflective surface 116 a, 116 b, and 116 c, all of which arecontemplated and possible within the context of the present disclosure.

Reflective surface type 230 could include a continuous mirror made up offirst flat mirror portion 118 a, a second flat mirror portion 118 b, anda third flat mirror portion 118 c that could be physically coupledtogether by way of a continuous mirror surface or another type ofcoupling structure. In other words, in some embodiments, the mirrorportions could be linked to one another and attached to the container112 by way of support 232. In such a scenario, the mirror portions neednot be individually supported or mounted. Instead, a single continuousmirror could be physically supported by a single support (e.g., support232).

Reflective surface type 240 could include a curved mirror portion 119with a corresponding curved reflective surface 116 d. The curved mirrorportion 119 could be curved in an axially symmetric manner (e.g., havinga cylindrical curvature). However, in other embodiments, curved mirrorportion 119 could be curved according to another shape.

FIG. 2D illustrates a photoresist structure 250, according to an exampleembodiment. FIG. 2D illustrates the photoresist structure 250 upondevelopment of the photoresist material 130. In particular, afterexposure of the angled structures 134 a, 134 b, 134 c, and 132, variousportions of the photoresist material 130 may be removed to revealsurfaces of the photoresist structure 250. In some embodiments, theangled structures 134 a, 134 b, and 134 c could have different mirrorangles with respect to the first surface 142 of the substrate 140. WhileFIG. 2D illustrates the photoresist structure 250 as having a certainshape, other shapes are possible and contemplated herein.

FIG. 2E illustrates an optical component 110, according to an exampleembodiment. FIG. 2E is an oblique view of a light input side of theoptical component 110. The optical component 110 could include acontainer 112. The optical component 110 could include a firstreflective surface 116 and a second reflective surface 270. The opticalcomponent 110 could also include a transparent top window 260 and atransparent bottom window 262.

FIG. 2F illustrates an optical component 110, according to an exampleembodiment. FIG. 2F is an oblique view of a light output side of theoptical component 110. The optical component 110 could include acontainer 112. As illustrated in FIG. 2F, the optical component 110could include a first reflective surface 116, a transparent top window260, and a transparent bottom window 262.

FIG. 3A illustrates a system 300, according to an example embodiment.System 300 could be similar or identical to system 100 and/or system200, as illustrated and described in relation to FIGS. 1 and 2A. Forexample, the system 300 could include a light source 10 and a container112 filled, at least partially, with light-coupling material 114. Thesystem 300 also could include a first reflective surface 116 and asecond reflective surface 270.

In an example embodiment, system 300 includes an aperture mask 160 thatcould be arranged between an exit surface (e.g., bottom surface 214) ofthe container 112. In such a scenario, light emitted from the lightsource 10 could be reflected from the first reflective surface 116 andthe second reflective surface 270 and impinge on the aperture mask 160.A portion of the reflected light may be transmitted through the openings162 in the aperture mask 160.

The light transmitted through the aperture mask 160 could expose thephotoresist material 130, which could overlay a first surface 142 of asubstrate 140. As described herein, the angles of the transmitted lightcould be controlled or manipulated so as to expose angled structures inthe photoresist material 130.

FIG. 3B illustrates a system 320, according to an example embodiment.System 320 could be similar or identical to system 100 and/or system200, as illustrated and described in relation to FIGS. 1 and 2A. Forexample, the system 320 could include a light source 10 and a container112 filled, at least partially, with light-coupling material 114. Thesystem 320 also could include a first reflective surface 116 and asecond reflective surface 270.

In some embodiments, system 320 may include the light source 10 beingarranged below (e.g., underneath) the container 112. As such, lightemitted from the light source 10 may be directed upward toward a bottomsurface 214 of the container 112.

In such scenarios, system 320 includes an aperture mask 160 that couldbe arranged within the container 112 along a bottom interior surface ofthe container. In such a scenario, light emitted from the light source10 could be incident on the aperture mask 160 and be transmitted towardthe reflective surfaces 116 and/or 270 by way of the openings 162. Aportion of the transmitted light may be reflected by reflective surfaces116 and/or 270 so as to expose the photoresist material 130, which couldoverlay a first surface 142 of a substrate 140.

FIG. 3C illustrates a system 330, according to an example embodiment.For example, system 330 could be similar or identical to system 100and/or system 200, as illustrated and described in relation to FIGS. 1and 2A. For example, the system 330 could include a light source 10 anda container 112 filled, at least partially, with light-coupling material114. The system 330 also could include a first reflective surface 116and a second reflective surface 270.

In some embodiments, system 330 may include the light source 10 beingarranged below (e.g., underneath) the container 112. As such, lightemitted from the light source 10 may be directed upward toward a bottomsurface 214 of the container 112.

In such scenarios, system 330 includes an aperture mask 160 that couldbe arranged in the container 112 and in proximity to the photoresistmaterial 130. For example, the aperture mask could be in soft or hardcontact with the photoresist material 130. In such a scenario, lightemitted from the light source 10 could be incident on the reflectivesurfaces 116 and/or 270. Reflected and transmitted light would beincident upon the aperture mask 160 and be transmitted toward thephotoresist material 130 by way of the openings 162 to expose thephotoresist material 130, which could overlay a first surface 142 of asubstrate 140. III. Example Optical Systems

FIGS. 4A and 4B illustrate an optical system 400 and portions thereof,according to an example embodiment. Optical system 400 may be a compactLIDAR system that incorporates optical light guide elements. Such aLIDAR system may be configured to provide information (e.g., point clouddata) about one or more objects (e.g., location, shape, etc.) in a givenenvironment. In an example embodiment, the LIDAR system could providepoint cloud information, object information, mapping information, orother information to a vehicle. The vehicle could be a semi- orfully-automated vehicle. For instance, the vehicle could be aself-driving car, an autonomous drone aircraft, an autonomous truck, oran autonomous robot. Other types of vehicles and LIDAR systems arecontemplated herein.

FIG. 4A illustrates a schematic block diagram of the optical system 400,according to an example embodiment. The optical system 400 includes asubstrate 410, a light-emitter device 420, and an optical waveguide 430.In some embodiments, the light-emitter device 420 could include a laserassembly that includes one or more laser bars. Additionally oralternatively, the optical system 400 could include a cylindrical lens422. In some examples, the cylindrical lens 422 could include an opticalfiber.

The optical waveguide 430 is arranged along a surface of the substrate410. The optical waveguide 430 includes at least one mirror surface 432.The optical waveguide 430 is configured to guide light emitted by thelight-emitter device 420. Such light may be guided within at least aportion of the optical waveguide 430 via total internal reflection.

In some embodiments, the at least one mirror surface 432 of the opticalwaveguide 430 may include a reflective material, such as a metalliccoating. In some embodiments, the metallic coating may include one ormore metals such as titanium, platinum, gold, silver, aluminum, and/oranother type of metal. In other embodiments, the at least one mirrorsurface 432 may include a dielectric coating and/or a dielectric stack.

In such scenarios, a portion of the guided light interacts with themirror surface 432 so as to direct reflected light into an environmentof the optical system 400. In some embodiments, the mirror surface 432could be arranged at at least one of 42 degrees, 45 degrees, or 48degrees with respect to the substrate 410.

The light-emitter device 420 may be configured to emit light towards acylindrical lens 422, which may help focus, defocus, direct, and/orotherwise couple the emitted light into the optical waveguide 430.

Optical system 400 is one of a variety of different optical systems thatmay include light guides such as optical waveguide 430 formed from aphotoresist material 130 or other optical materials. In an exampleembodiment, optical waveguide 430 could be coupled to a transparentsubstrate. In such scenarios, the mirror surface(s) 432 could beconfigured to direct light emitted by the light-emitter device 420towards the transparent substrate and thereafter into the environment ofthe optical system 400.

FIG. 4B illustrates a top view and side view of the optical system 400,according to an example embodiment. As illustrated in FIG. 4B, opticalwaveguide 430 could be similar or identical to photoresist structure 250as illustrated and described in relation to FIG. 2D.

As an example, the optical waveguide 430 could include three mirrorsurfaces 432 a, 432 b, and 432 c. The mirror surfaces 432 a, 432 b, and432 c could have different angles. For example, mirror surface 432 acould be oriented at a 42° mirror angle with respect to the surface ofsubstrate 410. Additionally or alternatively, mirror surface 432 b couldbe oriented at a 45° mirror angle with respect to the surface ofsubstrate 410. Yet further, mirror surface 432 c could be oriented at a48° mirror angle with respect to the surface of substrate 410. It willbe understood that other mirror angles (e.g., between 30° and 60°) arepossible and contemplated. Furthermore, it will be understood that whileFIG. 4B illustrates a particular arrangement of mirror surfaces 432, itwill be understood that other arrangements of the mirror surfaces 432and other elements of the optical waveguide 430 are possible andcontemplated.

In some embodiments, the optical system 400 could include alight-emitter device 420 and a cylindrical lens 422. The cylindricallens 422 could be arranged between the light-emitter device 420 and aninput surface 450 of the optical waveguide 430. The light-emitter device420 could be configured to emit emitted light 421 toward the cylindricallens 422.

For example, as illustrated in FIG. 4B, the light-emitter device 420 mayemit emitted light 421, which may be coupled into the optical waveguide430 via the input surface 450. In such a scenario, light portions 424 a,424 b, and 424 c may be reflected toward an environment via mirrorsurfaces 432 a, 432 b, and 432 c, respectively. Reflected light portions440 a, 440 b, and 440 c could be outcoupled by way of the substrate 410,which may be substantially transparent. The reflected light portions 440a, 440 b, and 440 c may interact with objects in the environment (e.g.,via reflection, absorption, and/or refraction).

Put another way, upon interacting with the cylindrical lens 422, variousportions of the emitted light 421 could be coupled into the opticalwaveguide 430. For example, a first light portion 424 a could interactwith mirror surface 432 a. In such a scenario, the first light portion424 a could be reflected from the mirror surface 432 a, forming firstreflected light 440 a. Additionally, a second light portion 424 b couldinteract with mirror surface 432 b. In such a scenario, the second lightportion 424 b could be reflected from the mirror surface 432 b, formingsecond reflected light 440 b. Furthermore, a third light portion 424 ccould interact with mirror surface 432 c. In such a scenario, the thirdlight portion 424 c could be reflected from the mirror surface 432 c,forming second reflected light 440 c.

As illustrated, first reflected light 440 a, second reflected light 440b, and third reflected light 440 c could be reflected at differentangles with respect to the surface of the substrate 410. For example,first reflected light 440 a, second reflected light 440 b, and thirdreflected light 440 c could be between ±6° with respect to the surfacenormal of the substrate 410. Other reflected angles are possible andcontemplated.

IV. Example Methods

FIG. 5 illustrates a method 500, according to an example embodiment. Itwill be understood that the method 500 may include fewer or more stepsor blocks than those expressly illustrated or otherwise disclosedherein. Furthermore, respective steps or blocks of method 500 may beperformed in any order and each step or block may be performed one ormore times. In some embodiments, some or all of the blocks or steps ofmethod 500 may relate to elements of system 100 and/or optical system400 as illustrated and described in relation to FIGS. 1, 4A, and 4D.

Block 502 includes placing a substrate near one end of an opticalcomponent, wherein photoresist material overlays at least a portion of afirst surface of the substrate, and wherein the optical componentcomprises: (i) a container containing a light-coupling material, and(ii) a reflective surface.

Block 504 includes causing a light source to emit light into the opticalcomponent, wherein the reflective surface reflects at least a firstportion of the emitted light to illuminate the photoresist material atthe one or more desired angles, thereby exposing at least a portion ofan angled structure in the photoresist material.

In some embodiments, the one or more desired angles could include one ormore reflective surfaces being oriented at at least one of: 42 degrees,45 degrees, and 48 degrees with respect to the first surface. It will beunderstood that other desired angles are contemplated and possiblewithin the scope of the present disclosure.

In some examples, the method may include overlaying an aperture mask onor near a surface of the optical component. The aperture mask couldinclude one or more openings, each opening corresponding to a respectivedesired structure in the photoresist material. At least a portion of theemitted light that is transmitted through each opening exposes therespective desired structure to which the opening corresponds.

In some embodiments, the aperture mask includes a first opening. In suchscenarios, the first opening is configured to allow the first portion ofthe emitted light to interact with a first portion of the reflectivesurface. The first portion of the reflective surface is configured toredirect the first portion of the emitted light to expose the at leastone angled structure.

In an embodiment, the method 500 may involve determining desiredstructures to fabricate, such as vertical structures and/or angledstructures. Additionally, the method 500 may involve determiningparameters of the desired structures. For example, the method 500 mayinvolve determining dimensions of the desired structures. Additionally,for the desired angled structures, the method 500 may involvedetermining a desired slope angle. For example, the desired slope anglemay be between 30-60 degrees with respect to a substrate surface.

As explained above, the desired slope angle of the angle structures maydetermine the mirror orientation angles. Accordingly, the method 500 mayalso involve determining the mirror orientation angles θ_(a), θ_(b),which may be determined using Snell's law. Snell's law states that aratio of the sines of the angles of incidence and refraction isequivalent to the reciprocal of a ratio of the indices of refraction,which is represented by the following formula:

$\begin{matrix}{\frac{\sin\theta_{2}}{\sin\theta_{1}} = \frac{n_{1}}{n_{2}}} & (1)\end{matrix}$

The desired angle of refraction in the photoresist material (e.g.,photoresist material 130) (θ₂), the refractive index of thelight-coupling material (e.g., light-coupling material 114) (n₁), andthe refractive index of the photoresist material (n₂) are known and maybe used to calculate a desired angle of incidence. For example, theangle of incidence may be within an angle range between 15 to 45 degrees(inclusive) from normal incidence. It will be understood that otherangles are possible and dynamically varying angles of incidence arepossible as well.

Based on the angle of incidence, the mirror orientation angles (e.g.,angles θ_(a), θ_(b), and/or θ_(c) as illustrated and described inrelation to FIG. 2A) may be calculated. In particular, the angles may becalculated such that the light reflected by the reflective surface(s)may be incident on the photoresist material with the desired angle ofincidence. Once the angles are calculated, the method 500 may alsoinvolve adjusting the adjustable coupling components (e.g., supports 210a, 210 b, and/or 210 c) such that the reflective surfaces are positionedat the desired angles.

The method 500 may also involve providing a wafer that includes thesubstrate (e.g., substrate 140) that is overlaid with the photoresistmaterial. In such scenarios, providing the substrate may involvepreparing the photoresist material by depositing a photoresist onto thesubstrate 140 followed by baking the photoresist material. Additionally,providing the wafer may include disposing a photoresist material ontothe wafer. Additionally, providing the wafer may involve aligning thewafer with the optical component. As explained herein, aligning thewafer may involve aligning fiducials on an exit surface (e.g., bottomsurface 214) with features on a photomask (e.g., photomask 170).

The method 500 may also involve causing the light source to emit lightdirected towards the optical component. For example, the light sourcemay emit light towards the optical component by way of a substantiallyuniform illumination intensity across a first surface of the opticalcomponent. In example systems where the light source is not positionedabove the optical component, the light from the light source may beredirected towards the optical component via one or more opticalelements (e.g., mirrors, light guides, etc.).

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other embodiments may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anillustrative embodiment may include elements that are not illustrated inthe Figures.

A step or block that represents a processing of information cancorrespond to circuitry that can be configured to perform the specificlogical functions of a herein-described method or technique.Alternatively or additionally, a step or block that represents aprocessing of information can correspond to a module, a segment, or aportion of program code (including related data). The program code caninclude one or more instructions executable by a processor forimplementing specific logical functions or actions in the method ortechnique. The program code and/or related data can be stored on anytype of computer readable medium such as a storage device including adisk, hard drive, or other storage medium.

The computer readable medium can also include non-transitory computerreadable media such as computer-readable media that store data for shortperiods of time like register memory, processor cache, and random accessmemory (RAM). The computer readable media can also includenon-transitory computer readable media that store program code and/ordata for longer periods of time. Thus, the computer readable media mayinclude secondary or persistent long term storage, like read only memory(ROM), optical or magnetic disks, compact-disc read only memory(CD-ROM), for example. The computer readable media can also be any othervolatile or non-volatile storage systems. A computer readable medium canbe considered a computer readable storage medium, for example, or atangible storage device.

While various examples and embodiments have been disclosed, otherexamples and embodiments will be apparent to those skilled in the art.The various disclosed examples and embodiments are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

1. A system comprising: an optical component configured to direct lightemitted by a light source to illuminate a photoresist material at one ormore desired angles so as to expose an angled structure in thephotoresist material, wherein the photoresist material overlays at leasta portion of a first surface of a substrate, and wherein the opticalcomponent comprises: a container containing a light-coupling materialthat is selected based in part on the one or more desired angles; and areflective surface arranged to reflect at least a first portion of theemitted light to illuminate the photoresist material at the one or moredesired angles.
 2. The system of claim 1, wherein the one or moredesired angles comprise at least one of: 42 degrees, 45 degrees, and 48degrees with respect to the first surface.
 3. The system of claim 1,wherein the one or more desired angles comprise at least one angleselected from an angle range between 30 degrees and 60 degrees withrespect to the first surface.
 4. The system of claim 1, wherein thereflective surface comprises a plurality of flat mirror portionscorresponding to the one or more desired angles.
 5. The system of claim1, wherein the reflective surface comprises one or more curved mirrorportions.
 6. The system of claim 1, further comprising an aperture maskplaced between the light source and the substrate, wherein the aperturemask comprises one or more openings, each opening corresponding to arespective desired structure in the photoresist material, wherein atleast a portion of the emitted light that is transmitted through eachopening exposes the respective desired structure to which the openingcorresponds.
 7. The system of claim 6, wherein the respective desiredstructure comprises at least one vertical structure and at least oneangled structure.
 8. The system of claim 7, wherein the aperture maskcomprises a first opening, wherein the first opening is configured toallow the first portion of the emitted light to interact with a firstportion of the reflective surface, wherein the first portion of thereflective surface is configured to redirect the first portion of theemitted light to expose the at least one angled structure.
 9. The systemof claim 7, wherein the aperture mask comprises a second opening,wherein the second opening is configured to allow a second portion ofthe emitted light to expose the at least one vertical structure.
 10. Thesystem of claim 1, wherein at least a portion of a first surface of thecontainer and at least a portion of a second surface of the containerare transparent, wherein the emitted light enters the container throughthe transparent portion of the first surface, and wherein the emittedlight illuminates the photoresist material through the transparentportion of the second surface.
 11. The system of claim 1, furthercomprising a photomask arranged in proximity to the photoresistmaterial, wherein the photomask is configured to define individualdesired structures in the photoresist material.
 12. The system of claim1, wherein the optical component further comprises a device configuredto remove stray light within the optical component.
 13. The system ofclaim 1, wherein the light source comprises an anisotropic collimatedlight source.
 14. The system of claim 1, wherein the light-couplingmaterial comprises at least one of: water, glycol, and glycerol.
 15. Thesystem of claim 1, wherein the substrate is immersed in thelight-coupling material such that the photoresist material is facing asecond surface of the container, wherein at least a portion of thesecond surface of the container is transparent, and wherein the emittedlight from the light source enters the container through the transparentportion of the second surface of the container.
 16. An optical systemcomprising: a substrate; a light-emitter device; and an opticalwaveguide arranged along a surface of the substrate, wherein the opticalwaveguide comprises a mirror surface, wherein the optical waveguide isconfigured to guide light emitted by the light-emitter device, wherein aportion of the guided light interacts with the mirror surface so as todirect reflected light into an environment of the optical system,wherein the mirror surface is arranged at between 30 degrees and 60degrees with respect to the substrate.
 17. A method comprising: placinga substrate near one end of an optical component, wherein photoresistmaterial overlays at least a portion of a first surface of thesubstrate, and wherein the optical component comprises: (i) a containercontaining a light-coupling material, and (ii) a reflective surface; andcausing a light source to emit light into the optical component, whereinthe reflective surface reflects at least a first portion of the emittedlight to illuminate the photoresist material at one or more desiredangles, thereby exposing at least a portion of an angled structure inthe photoresist material.
 18. The method of claim 17, wherein the one ormore desired angles comprise at least one of: 42 degrees, 45 degrees,and 48 degrees with respect to the first surface.
 19. The method ofclaim 17, wherein the method further comprises: overlaying an aperturemask on or near a surface of the optical component, wherein the aperturemask comprises one or more openings, each opening corresponding to arespective desired structure in the photoresist material, wherein atleast a portion of the emitted light that is transmitted through eachopening exposes the respective desired structure to which the openingcorresponds.
 20. The method of claim 17, wherein the aperture maskcomprises a first opening, wherein the first opening is configured toallow the first portion of the emitted light to interact with a firstportion of the reflective surface, wherein the first portion of thereflective surface is configured to redirect the first portion of theemitted light to expose the at least one angled structure.